Insulated electrical conductor



Se t. 7, 1948. c. c. SMlTH 2,448,633

INSULATED ELECTRICAL CONDUCTOR Filed June 23, 1943 can/M55 ACE/7175 m'w INVENTOR CC. SMITH pr A T TORNEY Patented Sept. 7, 1948 UNITED STATES PATENT OFFICE INSULATED ELECTRICAL CONDUCTOR I Charles C. Smith, Cranford, N. J., assignor to Western Electric Company, Incorporated, New York, N. Y., a corporation of New York Application June 23, 1943, Serial No. 491,968

2 Claims. 1

This invention relates to electrical conductors and more particularly to electrical conductors insulated with cellulose acetate rayon.

Cellulose acetate rayon is becoming a popular substitute for silk as an insulating material on electrical conductors in the communication arts. However, its smooth fiberless nature and its continuous extruded filaments have rendered it difficult for serving to a conductor core under the known methods employed for serving silk or the like.

Objects of the invention are to provide an electrical conductor uniformly insulated with an inexpensive insulating material having high insulating properties.

With this and other objects in view, the invention comprises a conductor insulated with a single end of a multiplicity of filaments of cellulose acetate rayon held against fraying by the existence of a low twist therein and a lubricant added to the external portions thereof.

Other objects and advantages will be apparent from the iollowing detailed description when considered in conjunction with the accompanying drawing, wherein Figs, 1 and 2 are fragmentary detailed views of the insulated conductor;

Fig. 3 is an enlarged lateral sectional view oi! the insulated conductor, this view being taken along the line 22 of Fig. 1, and

' Fig. 4 is a view of the insulating material-illustrating the low twist of the filaments rpresent therein.

In the present invention the result obtained, namely the insulated conductor, and the condition of the insulating material on the conductor depend greatly upon various preceding factors, namely the nature of the material, :the number of ends of which it is composed, the amount of twist of the filament therein. the effect of the various parts of the serving machine upon the material while the material is served on the conductor, and the tension in the material during the various stages through which it travels while being served on the conductor core. For example, it has been found that in serving multiple end yarn of cellulose acetate rayon yarn on a conductor, the passing of the yarn about conventional guides, prior to its reaching the conductor, causes the ends of the yarn to run with varying amounts of tension, and as a result of this variation rthe yarn ofttimes separates into loose and taut ends. When this condition exists the taut yarn end, carrying the full tension intended rior all ends, frequently breaks due to overloading.

(The loose end or ends in the same instance ofttimes leave their intended path and catch on projecting objects, causing the loose ends of the yarn to Irequently break also. Each time a yarn breaks or portions thereof break, the operator is required to stop the serving 'head, thus resulting in the loss of time and also the loss of material required in the removal of the unsatisfactori-ly insulated portion of the conductor, brazing the ends of the conductors and tying the ends of the yarn 'for further operation of the serving head.

To eliminate the difiiculty existing with the yarn =formed of the plurality of ends, a single end yarn, for example, a nine hundred (900) denier yarn with no twist, was run through a machine for serving onto a conductor. This yarn, due to the absence of any means to hold the untwisted filaments into a single group, separated into two ends each approximately one-half of the original band and the same results followed which existed in the serving of a yarn formed of a plurality of ends. A nine hundred (900) denier yarn with approximately three twists per inch was served to an electrical conductor and in this instance numerous diiiiculties described as existing with the multiple end yarn and the single end yarn with no twist, were eliminated but the result obtained was unsatisfactory due to the roughness of the material on the conductor, there appearing hills and valleys in the material due to the unsatisfactory spreading characteristics of the material resulting from the high twist present therein.

The present embodiment includes a material formed of cellulose :acetate yarn, which may be readily served to the conductor, and provides a highly satisfactory insulated covering therefor. This material, indicated at Ill, is, in the present embodiment, nine hundred (900) denier single end yarn with a low twist from .3 to .75 turn per inch and having a lubricating finish consisting of 3% to 4% transil oil. The existence of the lubricating agent, namely the transil oil, serves to remove the friction between the material and the parts of the machine over which it travels in advancing to the core, eliminating also the result of filament breakage at these points. Furthermore, the low twist present in the yarn permits the yarn to spread sufficiently when served to the conductor to eliminate the existence of hills and valleys therein. It will be noted, by viewing Figs. 1 and 2, that the edges of the convolutions of the material overlap, as indicated at II, when being served to the conductor H. with the low twist and the spreading inherent feature in uniform covering of cellulose acetate material inw cluding the nine hundred (900) denier yarn of low twist filamentsserved to the conductor with the edges overlapping for the interlocking of the filaments of the material. The illustrations in Figs. 3 and 4 show the low twist present in the 15 yarn, the dotted and solid diagonal lines in Fig. 4 following the course of one filament, the lines, of the other filaments not being shown, as it was thought that in this manner the condition of the twist could be more clearly illustrated.

It is not possible to illustrate the interlocking arrangement of the filaments at the overlapping edges of the material, but it should be understood that the spreading characteristics of the material, due to the low twist of the filaments thereof and the presence of the lubricating agent on the outer surface of the yarn, make possible the interiaying of the filaments of the meeting edges, eliminating fraying or unwinding of the material from the conductor at any point where the conductor should be out. However, if desired the material may be readily removed from a portion of the conductor to bare an end thereof for electrical connection with another conductor or an electrical unit.

Although specific improvements of the inven- 35 tion have been shown and described, it will be understood that they are but illustrative and that various modifications may be made therein without departing from the scope and spirit of 40 this invention as defined by the appended claims.

What is claimed is:

1. An insulated electrical conductor comprising a, conductor core, and-a single end of cellulose acetate rayon yarn spirally wound with overlapping edges on the coreand formed of a multiplicity of continuous filaments held in a uniformly complete group free to spread into a uniform cover with interlocking filaments at the overlapping edges by a low twist in the yarn from .3 to .75 turn per inch.

2. An insulated electrical conductor comprising a conductor core, a single end of cellulose acetate rayon yarn spirally wound with overlapping edges on the core and formed of a multiplicity of continuous filaments held in a uniformly complete group free to spread into a uniform cover with interlocking filaments at the overlapping edges by a low twist in the yarn from .3 to .75 turn per inch, and a lubricant disposed on the external filaments of the yarn to facilitate in the interlocking of the filaments at the overlapping edges.

CHARLES C. SMITH.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 0 Number Name Date 1,966,509 Lynn July 17, 1934 2,089,188 Dreyfus et al Aug. 10, 1937 2,103,245 Budd Dec. 28, 1937 2,132,492 Parker Oct. 11, 1938 2,234,353 Quinlan Mar. 11, 1941 FOREIGN PATENTS Number Country Date 448,307 Great Britain June 5, 1936 512,002 Great Britain Aug. 28, 1939 

